When a firearm is fired, minute particles are invariably worn away, from both the firearm barrel and the projectile. Some particles will adhere to the barrel, and the rest are expelled with the projectile.
For hundreds of years lead has been the most popular material for projectiles. However, in recent years, the public has become increasingly vocal about the health problems caused by poisons such as lead. Law enforcement officials and others who frequently use practice ranges run the greatest risk of direct exposure to the lead particles produced by the use of lead shot. It is thus desirable to reduce the number of particles worn from the projectile as it is expelled.
Particles worn from the barrel have historically presented a problem which is primarily manifested as loss of accuracy after many firings. Excessive wear resulting from many firings or from the use of unauthorized propellant, such as in muzzle loaders, can also present a safety hazard if failure of the forcing cone or barrel occurs.
These health and safety problems are related in that their eventual solution depends upon determining the number and type of particles expelled from a firearm. For example, analysis of the number and type of particles expelled after a single shot can be used to determine the effectiveness of treating the barrel or the projectile, such as by cladding. Statistics collected on the number and type of particles generated during a series of test firings can be used to predict the longevity of different barrel and shot material combinations.
Several techniques for analyzing barrel wear are presently in use. These include fluoroscopic examination, observation of decreasing accuracy, precision gauging, and other elaborate methods. However, because of their expense and logistic complexity, these known techniques do not easily lend themselves to obtaining relative data over many firings.
One wear analysis technique, developed for evaluating the condition of oil lubricated engines, does provide data without these disadvantages. It is based on direct examination of the quantity, size, and rate of increase of contaminants in the lubricating oil. See, for example, U.S. Pat. No. 4,448,887 issued to Kauffman, et al. Examination can be accomplished in several ways, such as visually, or by spectroscopy. However, a method known as ferrography is a particularly convenient and inexpensive way to determine these parameters. See U.S. Pat. No. 4,047,814 issued in September, 1977 to Westcott.
If ferrography could be applied to accurately determine the quantity, size, and type of wear particles from a firearm blast, an important tool for appraising various combinations of projectiles and methods of reducing barrel wear would exist. Information about the composition of the wear particles could also be used to interpret the nature of the wear process.